Charlton · ADU cost
What it costs to build an ADU in Charlton, NY
An 800 sq ft accessory dwelling unit in Charlton runs roughly $200k–260k, or about $249–327/sq ft, and that per-square-foot figure sits deliberately above the $204–268/sq ft a full house costs here. An ADU still needs one whole kitchen, one whole bath, its own service panel and its own heating plant no matter how small you draw it, and those costs do not shrink with the floor plan, so they land on half the square footage and push the rate up. Whether the town will let you build one is a separate question from what it costs, and it gets answered parcel by parcel rather than townwide, since the Town of Charlton maps 3 districts that treat accessory units differently from one another, so read the table below as a starting point rather than a verdict.
ADU cost by size in Charlton
Standard finish, slab on grade, on a flat and clear part of the lot, general-contractor margin included. These are structure costs at Saratoga County pricing, before the service and septic work a second dwelling can trigger.
| Size | Type | $ / sq ft | Estimated total |
|---|---|---|---|
| 400 sq ft | Studio | $331–$433 | $130k–175k |
| 600 sq ft | One bedroom | $276–$362 | $165k–215k |
| 800 sq ft | One bedroom, larger | $249–$327 | $200k–260k |
| 1,000 sq ft | Two bedroom | $233–$305 | $235k–305k |
400 sq ft — One room plus a bath. Garage conversions and small backyard cottages land here.
600 sq ft — The most common detached build - a real bedroom, full kitchen, one bath.
800 sq ft — Room for a proper living area. Still a single bath and one kitchen.
1,000 sq ft — About as large as most codes allow an accessory unit to go.
Why the rate is higher than a house
The systems below are priced for an 800 sq ft unit. The middle column is what each system would cost if it simply shrank with the floor plan; the left column is what it actually costs once you account for the equipment a dwelling needs one of regardless of size. The gap between the two columns is the whole reason small builds price the way they do.
| System | $ / sq ft in an ADU | If it scaled with floor area | Fixed per unit |
|---|---|---|---|
| Site work | $7–$11 | $7 | — |
| Foundation | $16–$23 | $16 | — |
| Framing | $25–$32 | $25 | — |
| Envelope - roof, siding, windows | $32–$41 | $32 | — |
| Plumbing | $28–$34 | $16 | 55% |
| Electrical | $18–$24 | $13 | 35% |
| HVAC | $23–$28 | $15 | 45% |
| Insulation | $7–$9 | $7 | — |
| Interior finishes | $32–$43 | $27 | 15% |
| Millwork & cabinetry | $18–$28 | $11 | 55% |
The fixed-per-unit share is a modeling assumption, not a figure from the code: it is our estimate of how much of each system's budget buys equipment a dwelling needs exactly one of - a kitchen rough-in, a bath group, a service panel, a heating plant - and therefore does not shrink when the unit does. Site work, foundation, framing, envelope and insulation are treated as scaling straight with floor area, which understates the premium slightly, because a small building carries more envelope per square foot of floor than a large one.
What the Charlton code says about accessory units
Whether you can build one, and how large, is decided by the district your parcel sits in rather than by the town as a whole. The table shows how each mapped district treats ADUs alongside the lot and setback standards a second unit still has to fit inside. District boundaries and conditions vary, so treat it as a starting point and confirm the district that applies to your parcel.
| District | Min lot | Setbacks F / S / R | Max height | ADU |
|---|---|---|---|---|
| Rural District (the Town's principal district: a private dwelling — including one with a customary home occupation — on 4 ACRES WITH 2 ACRES OF BUILDABLE LAND, 400 ft of lot width AND 400 ft of frontage, a 30 FT maximum height, a 60 ft front yard, 15 ft minimum side yard with 40 ft for both sides combined, and a 50 ft rear yard. MINIMUM LOT AREA IS TWO REQUIREMENTS, NOT ONE: '4 acres WITH 2 ACRES BUILDABLE LAND'. A four-acre parcel that cannot show two acres of buildable land does not qualify, so wetland, slope and floodplain reduce the effective yield before any yard is measured. Table IV-2 notes 1 and 2 point to Article VII for special-permit dimensions and to Article VIII and the Subdivision Regulations for the cases where less than four acres or less than 400 ft of frontage or width is permitted — check those before concluding a smaller parcel is unbuildable. The side yard is a pair and both figures bind: a minimum for ONE side and a larger minimum for the TWO COMBINED. sideSetback records the one-side figure. THE 400 FT WIDTH AND FRONTAGE ARE AS BINDING AS THE ACREAGE and will disqualify many four-acre parcels outright — a square four-acre lot is only about 417 ft on a side, so the district effectively requires near-square or wider geometry. ALL OTHER NON-AGRICULTURAL USES ARE HELD TO A MUCH DEEPER ENVELOPE on the same lot: 40 ft height rather than 30, and 100 ft front, 100 ft total side, 50 ft minimum side and 50 ft rear — so a non-residential building sits roughly twice as far from every boundary as a house does. THE PERCENTAGE COLUMN IS NOT LOT COVERAGE. Table IV-2's last column is headed 'Maximum Percentage of ACCESSORY BUILDING Coverage' — it caps accessory buildings only and says nothing about the principal dwelling. Charlton states NO principal-building coverage limit anywhere, so maxLotCoverage is null by design. Recording the 5% or 10% figure as lot coverage would understate the buildable footprint by an order of magnitude and is the single easiest mistake to make in this code. Accessory buildings here are capped at 5% of the lot.) | 4 ac | 60 / 15 / 50 ft | 30 ft | As of right |
| Agricultural District (dimensionally almost identical to Rural — a private dwelling on 4 ACRES WITH 2 ACRES BUILDABLE, 400 ft width and 400 ft frontage, 30 ft height, 60 ft front and 50 ft rear — WITH ONE DELIBERATE DIFFERENCE THAT IS EASY TO MISS: THE SIDE YARDS ARE FAR DEEPER. A dwelling in the Agricultural District needs a 40 FT MINIMUM SIDE YARD with 100 FT FOR BOTH SIDES COMBINED, against Rural's 15 ft and 40 ft. That is more than double the one-side figure and two and a half times the combined, and it is the Town separating houses from working farmland rather than from each other. The side yard is a pair and both figures bind: a minimum for ONE side and a larger minimum for the TWO COMBINED. sideSetback records the one-side figure. MINIMUM LOT AREA IS TWO REQUIREMENTS, NOT ONE: '4 acres WITH 2 ACRES BUILDABLE LAND'. A four-acre parcel that cannot show two acres of buildable land does not qualify, so wetland, slope and floodplain reduce the effective yield before any yard is measured. Table IV-2 notes 1 and 2 point to Article VII for special-permit dimensions and to Article VIII and the Subdivision Regulations for the cases where less than four acres or less than 400 ft of frontage or width is permitted — check those before concluding a smaller parcel is unbuildable. Non-agricultural uses take the same 40 ft height and 100 ft front, 100 ft total side, 50 ft side and 50 ft rear as in Rural, and per Table IV-2 note 3 they additionally REQUIRE TOWN OF CHARLTON PLANNING BOARD APPROVAL (Appendix B-5) — a review requirement that does not attach to the equivalent Rural uses. Agricultural operations themselves sit outside this row. THE PERCENTAGE COLUMN IS NOT LOT COVERAGE. Table IV-2's last column is headed 'Maximum Percentage of ACCESSORY BUILDING Coverage' — it caps accessory buildings only and says nothing about the principal dwelling. Charlton states NO principal-building coverage limit anywhere, so maxLotCoverage is null by design. Recording the 5% or 10% figure as lot coverage would understate the buildable footprint by an order of magnitude and is the single easiest mistake to make in this code. Accessory buildings capped at 5%.) | 4 ac | 60 / 40 / 50 ft | 30 ft | As of right |
| Historic Overlay District (adopted under Local Law 2 of 1973 and mapped in Appendix A, with review by the Historic District Commission under Appendix B-3. ITS USES ARE 'SAME AS RURAL (R)' BUT ITS DIMENSIONS ARE MATERIALLY MORE PERMISSIVE, WHICH IS THE OPPOSITE OF WHAT AN OVERLAY USUALLY DOES: 2 ACRES with 2 acres buildable against Rural's 4, only 100 FT of lot width and 100 ft of frontage against Rural's 400, and a 30 ft front yard against 60. Height stays at 30 ft, the minimum side yard at 15 ft with 40 ft combined, and the rear yard at 50 ft. So the Historic Overlay HALVES the lot requirement and QUARTERS the width and frontage — it protects the historic hamlet pattern by permitting the small, close-set lots that pattern actually consists of, rather than by imposing extra bulk restrictions. Anyone assuming an overlay must be more restrictive will badly misjudge a Charlton historic parcel. THE TRADE IS PROCEDURAL RATHER THAN DIMENSIONAL: development here goes through the Historic District Commission, so the constraint is design review, not lot geometry. THE PERCENTAGE COLUMN IS NOT LOT COVERAGE. Table IV-2's last column is headed 'Maximum Percentage of ACCESSORY BUILDING Coverage' — it caps accessory buildings only and says nothing about the principal dwelling. Charlton states NO principal-building coverage limit anywhere, so maxLotCoverage is null by design. Recording the 5% or 10% figure as lot coverage would understate the buildable footprint by an order of magnitude and is the single easiest mistake to make in this code. Accessory buildings are capped at 10% here, double the 5% allowed in Rural and Agricultural — consistent with the smaller lots. The side yard is a pair and both figures bind: a minimum for ONE side and a larger minimum for the TWO COMBINED. sideSetback records the one-side figure.) | 2 ac | 30 / 15 / 50 ft | 30 ft | As of right |
Size limits on record in Charlton
Where the code states a size cap, it decides which row of the cost table above actually applies to you. These are the caps recorded for Charlton:
- Rural District (the Town's principal district: a private dwelling — including one with a customary home occupation — on 4 ACRES WITH 2 ACRES OF BUILDABLE LAND, 400 ft of lot width AND 400 ft of frontage, a 30 FT maximum height, a 60 ft front yard, 15 ft minimum side yard with 40 ft for both sides combined, and a 50 ft rear yard. MINIMUM LOT AREA IS TWO REQUIREMENTS, NOT ONE: '4 acres WITH 2 ACRES BUILDABLE LAND'. A four-acre parcel that cannot show two acres of buildable land does not qualify, so wetland, slope and floodplain reduce the effective yield before any yard is measured. Table IV-2 notes 1 and 2 point to Article VII for special-permit dimensions and to Article VIII and the Subdivision Regulations for the cases where less than four acres or less than 400 ft of frontage or width is permitted — check those before concluding a smaller parcel is unbuildable. The side yard is a pair and both figures bind: a minimum for ONE side and a larger minimum for the TWO COMBINED. sideSetback records the one-side figure. THE 400 FT WIDTH AND FRONTAGE ARE AS BINDING AS THE ACREAGE and will disqualify many four-acre parcels outright — a square four-acre lot is only about 417 ft on a side, so the district effectively requires near-square or wider geometry. ALL OTHER NON-AGRICULTURAL USES ARE HELD TO A MUCH DEEPER ENVELOPE on the same lot: 40 ft height rather than 30, and 100 ft front, 100 ft total side, 50 ft minimum side and 50 ft rear — so a non-residential building sits roughly twice as far from every boundary as a house does. THE PERCENTAGE COLUMN IS NOT LOT COVERAGE. Table IV-2's last column is headed 'Maximum Percentage of ACCESSORY BUILDING Coverage' — it caps accessory buildings only and says nothing about the principal dwelling. Charlton states NO principal-building coverage limit anywhere, so maxLotCoverage is null by design. Recording the 5% or 10% figure as lot coverage would understate the buildable footprint by an order of magnitude and is the single easiest mistake to make in this code. Accessory buildings here are capped at 5% of the lot.)Floor area may not exceed 1,000 sq ft INCLUDING BASEMENTS AND GARAGES, with a minimum of 600 sq ft of livable space
- Agricultural District (dimensionally almost identical to Rural — a private dwelling on 4 ACRES WITH 2 ACRES BUILDABLE, 400 ft width and 400 ft frontage, 30 ft height, 60 ft front and 50 ft rear — WITH ONE DELIBERATE DIFFERENCE THAT IS EASY TO MISS: THE SIDE YARDS ARE FAR DEEPER. A dwelling in the Agricultural District needs a 40 FT MINIMUM SIDE YARD with 100 FT FOR BOTH SIDES COMBINED, against Rural's 15 ft and 40 ft. That is more than double the one-side figure and two and a half times the combined, and it is the Town separating houses from working farmland rather than from each other. The side yard is a pair and both figures bind: a minimum for ONE side and a larger minimum for the TWO COMBINED. sideSetback records the one-side figure. MINIMUM LOT AREA IS TWO REQUIREMENTS, NOT ONE: '4 acres WITH 2 ACRES BUILDABLE LAND'. A four-acre parcel that cannot show two acres of buildable land does not qualify, so wetland, slope and floodplain reduce the effective yield before any yard is measured. Table IV-2 notes 1 and 2 point to Article VII for special-permit dimensions and to Article VIII and the Subdivision Regulations for the cases where less than four acres or less than 400 ft of frontage or width is permitted — check those before concluding a smaller parcel is unbuildable. Non-agricultural uses take the same 40 ft height and 100 ft front, 100 ft total side, 50 ft side and 50 ft rear as in Rural, and per Table IV-2 note 3 they additionally REQUIRE TOWN OF CHARLTON PLANNING BOARD APPROVAL (Appendix B-5) — a review requirement that does not attach to the equivalent Rural uses. Agricultural operations themselves sit outside this row. THE PERCENTAGE COLUMN IS NOT LOT COVERAGE. Table IV-2's last column is headed 'Maximum Percentage of ACCESSORY BUILDING Coverage' — it caps accessory buildings only and says nothing about the principal dwelling. Charlton states NO principal-building coverage limit anywhere, so maxLotCoverage is null by design. Recording the 5% or 10% figure as lot coverage would understate the buildable footprint by an order of magnitude and is the single easiest mistake to make in this code. Accessory buildings capped at 5%.)Floor area may not exceed 1,000 sq ft INCLUDING BASEMENTS AND GARAGES, with a minimum of 600 sq ft of livable space
- Historic Overlay District (adopted under Local Law 2 of 1973 and mapped in Appendix A, with review by the Historic District Commission under Appendix B-3. ITS USES ARE 'SAME AS RURAL (R)' BUT ITS DIMENSIONS ARE MATERIALLY MORE PERMISSIVE, WHICH IS THE OPPOSITE OF WHAT AN OVERLAY USUALLY DOES: 2 ACRES with 2 acres buildable against Rural's 4, only 100 FT of lot width and 100 ft of frontage against Rural's 400, and a 30 ft front yard against 60. Height stays at 30 ft, the minimum side yard at 15 ft with 40 ft combined, and the rear yard at 50 ft. So the Historic Overlay HALVES the lot requirement and QUARTERS the width and frontage — it protects the historic hamlet pattern by permitting the small, close-set lots that pattern actually consists of, rather than by imposing extra bulk restrictions. Anyone assuming an overlay must be more restrictive will badly misjudge a Charlton historic parcel. THE TRADE IS PROCEDURAL RATHER THAN DIMENSIONAL: development here goes through the Historic District Commission, so the constraint is design review, not lot geometry. THE PERCENTAGE COLUMN IS NOT LOT COVERAGE. Table IV-2's last column is headed 'Maximum Percentage of ACCESSORY BUILDING Coverage' — it caps accessory buildings only and says nothing about the principal dwelling. Charlton states NO principal-building coverage limit anywhere, so maxLotCoverage is null by design. Recording the 5% or 10% figure as lot coverage would understate the buildable footprint by an order of magnitude and is the single easiest mistake to make in this code. Accessory buildings are capped at 10% here, double the 5% allowed in Rural and Agricultural — consistent with the smaller lots. The side yard is a pair and both figures bind: a minimum for ONE side and a larger minimum for the TWO COMBINED. sideSetback records the one-side figure.)Floor area may not exceed 1,000 sq ft INCLUDING BASEMENTS AND GARAGES, with a minimum of 600 sq ft of livable space
Costs an ADU adds that a house does not
- Septic and water A second dwelling adds bedrooms to the design flow, which on an unsewered parcel often means expanding or replacing the existing system rather than tapping it. This is the single most common reason an ADU budget moves after design, and it is site-specific enough that no model should quote it - get it evaluated early.
- Utility service National Grid territory. A detached unit needs power run to it, and whether it goes on its own meter or subfeeds the main house changes both the cost and the permit path.
- Access and parking Many codes require an added parking space for the accessory unit, and a detached unit usually needs a driveway extension or a path, both of which count against a lot-coverage or impervious-surface cap.
- Short-term rentalsNo local short-term-rental law on record - which is not the same as permission. No short-term-rental provision exists in the Town of Charlton Zoning Law, and this is confirmed against the CURRENT text: the operative law is the Zoning Law ADOPTED JANUARY 26, 2026, whose Section 4 repeals and replaces the April 2025 law and every prior version in their entirety. The law defines no short-term rental or vacation rental use and creates no registration or licensing requirement — a notable omission in a 2025 rewrite, since most codes of that vintage address it one way or the other. THE ONE ENUMERATED TRANSIENT USE IS THE BED AND BREAKFAST, defined as a private residential structure, EITHER OWNER-OCCUPIED OR UNDER RESIDENT MANAGEMENT, offering lodging for compensation INCIDENTAL TO THE RESIDENTIAL USE, and limited in number of rooms. It is a SITE PLAN REVIEW (SPR) use in all three districts, and where a bed and breakfast is proposed as part of a farm operation, additional provisions apply. Note that the law's definition of 'dwelling' expressly EXCLUDES the duplex, multiple dwelling, mobile home and TOURIST HOME — so a tourist home is affirmatively outside the definition of a dwelling rather than merely unlisted, which is a stronger signal than most codes give. Recorded 'unknown' rather than 'prohibited' because the Town has not legislated on short-term rental specifically and whole-house rental of a permitted private dwelling is arguably the residential use itself — but note the bed-and-breakfast definition's 'incidental to the residential use' language points away from whole-house commercial rental. Absence of a found STR provision is NOT permission. Get a written answer from the Zoning Enforcement Officer at (518) 384-0152 before underwriting short-term rental income. Separately, New York State has required every short-term-rental host to register the unit with the State through the county registry since 2025, regardless of what the municipality allows, and Saratoga County HAS adopted a county-level short-term-rental programme: a 3% occupancy tax and a MANDATORY county registry, covering any room or space in a dwelling let for under 30 consecutive days. Registration runs two years, an unregistered host faces fines of up to $500, and the booking platform is separately liable for processing an unregistered listing — so Airbnb and Vrbo will delist. The City of Saratoga Springs runs its own registry alongside it. Separate question from whether you can build the unit.
- Building dept(518) 384-0152
Sizing up a specific parcel in Charlton?
Aldo pulls the exact zoning district, setbacks, and build feasibility for any parcel — before you buy. Enter your email to open Aldo and run your free report.
Building a full house instead?
A standard-finish house in Charlton runs $204–268/sq ft, about $370k–480k at 1,800 sq ft , plus roughly $6,108 for a conforming lot. See what it costs to build a house in Charlton.
ADU cost in nearby towns
All Saratoga County towns: Mechanicville (City) · Saratoga Springs (City) · Ballston · Clifton Park · Corinth · Day · Edinburg · Galway · Greenfield · Halfmoon · Malta · Milton · Moreau · Northumberland · Providence · Saratoga · Stillwater · Waterford · Wilton · Ballston Spa (Village) · Corinth (Village) · Round Lake (Village) · Schuylerville (Village) · South Glens Falls (Village) · Stillwater (Village) · Victory (Village) · Waterford (Village)
More on Charlton: Can you build an ADU here? · Zoning for new construction · Saratoga County build cost
ADU cost in Charlton: common questions
How much does it cost to build an ADU in Charlton, NY?
An 800 sq ft accessory dwelling unit in Town of Charlton runs roughly $200k–260k at a standard finish, general-contractor margin included. A 400 sq ft studio runs about $130k–175k. Those are structure costs on an easy site and do not include the septic, water or electrical service work a second unit often triggers.
Why does an ADU cost more per square foot than a house in Charlton?
Because a lot of a dwelling's cost is per dwelling, not per square foot. One kitchen, one bath group, one service panel and one heating plant cost about the same in an 800 sq ft cottage as in a 1,800 sq ft house, so on the smaller unit they get spread over less than half the floor area. That is why an ADU here prices at $249–327/sq ft against $204–268/sq ft for a full house, even though it is the same trades doing the same work.
Are ADUs allowed in Charlton?
Town of Charlton has 3 districts. All districts allow ADUs. Check the specific address with the free ADU checker or confirm with the building department at (518) 384-0152 before you spend money on design.
Can I rent an ADU in Charlton short term?
No local short-term-rental law on record - which is not the same as permission for Town of Charlton. ADU rules and short-term-rental rules are set separately, so a unit you are allowed to build is not automatically one you are allowed to rent nightly. Confirm both before you underwrite the build on short-term-rental income.
ADU costs are modeled estimates in current 2026 dollars at the Saratoga County regional index, general-contractor margin included, derived from Offsite's cost engine with a stated adjustment for the equipment a dwelling needs one of regardless of size. They are planning numbers for decision-support only - not a bid, quote, or guarantee, and not legal, architectural or engineering advice. They cover the structure and exclude septic expansion, utility service runs, site work beyond a flat and clear pad, and permit fees. ADU eligibility, size, owner-occupancy and permit conditions in the Town of Charlton vary by district and often carry exceptions this page does not show; zoning last reviewed 2026-08-01; verify with the building department at (518) 384-0152 before relying on any answer. Sources: Offsite / Aldo cost engine (costEngine.js + constants.js); zoning dataset (municipalData.js).